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Where did option B) Light Magic (8%) from my text go?! :)
By the time your Wing is level 20-25, Dyrael will already be level 25-30! You're probably playing on a medium difficulty level, not a hard one.
Regarding the difficulty, I play on Veteran with humans in the original Heroes 3.1 on random maps or in duels. There's no need to belittle opponents you don't know personally or haven't played with, and therefore don't know their abilities. Personally, this character development seems very dependent on a lucky combination of skills. If there's no mentor and good skills don't drop, the game will be lost, while the development methods described here allow for any scenario.